Cardiac resynchronization therapy (CRT) using a bi-ventricular pacemaker is an important treatment option for patients with drug-refractory heart failure and evidence of ventricular dyssynchrony. However, using current selection criteria and implantation techniques, 30-40% of patients undergoing CRT are non-responsive to the treatment. Because CRT is invasive, costly, has significant associated risks, and requires lifelong need of pacing device, there is a clear need for better methods to optimize the treatment. Multiple factors influence patient response to CRT including poor selection criteria and/or non-optimal device implementation. In the implementation of CRT, the position of the left ventricular (LV) pacing lead has a significant role in determining patient response. The overall goals of this project are: 1) to develop an MRI- based methodology to plan and locate the LV pacing lead in the area of latest contraction and 2) test the methodology on a group of patients undergoing CRT.